A high resolution mass spectrometer with high field magnet fast atom bombardment ion source, and rapid switching negative ion capability will be purchased for operation by the University of Illinois Mass Spectrometry Laboratory and employed in studying organic and organometallic compounds hitherto intractable due to their lack of volatility or thermal instability. Major users of the high field FAB mass spectrometer will be K. L. Rinehart, E. Oldfield, J. A. Katzenellenbogen, I. C. Gunsalus, N. J. Leonard, and O. C. Uhlenbeck, who will employ the instrument in their studies of high molecular weight antibiotics, marine natural products, phospholipids and glycolipids, oligonucleotides and analogs of nucleosides, cytochrome cleavage peptides and peptide derivatives of antitumor agents. Additional users will employ the high spectrometer in studies of organometallic aggregate, metal complexes of proteins and porphyrins, halogenating enzymes, methanogen coenzymes, roteinase products and complexes of hypervalent non-metallic elements. The high field spectrometer will also be used in studies designed to develop, test, and extend the FAB technique and for electrohydrodynamic ionization experiments on polymers.